Program Director/Principal Investigator (Last, First, Middle): Gantz, Bruce J. PROJECT SUMMARY ? PROJECT 3 The most important deficit faced by people with hearing impairment is understanding acoustic information? particularly speech?in noisy real-world environments. The central goal of this project is to understand the cognitive and neural bases of hearing impaired listeners' abilities to detect complex auditory objects in simulations of noisy real-life environments. Work on normal hearing listeners has identified fundamental cognitive and cortical mechanisms for perceiving auditory objects in noisy backgrounds, and there are established cortical mechanisms for perceiving of speech in noise. In both cases mechanisms in auditory cortex are active during the abstraction of complex objects from noisy backgrounds, and provide input into networks that allow further perceptual, attentional and semantic analysis. These brain networks have not yet been characterized in hearing impaired listeners, and it is not clear if auditory object detection contributes to speech perception in a way that cannot be predicted by peripheral hearing alone. Aim 1 applies a new measure of the ability to detect complex (non-speech) auditory objects in noise, and relates this to more standard speech in noise perception in a range of hearing impaired listeners. This is done to determine whether of speech in noise in hearing impaired listeners depends on mechanisms for cross-frequency grouping and examine how that dependence differs in patients with impaired acoustic hearing or a CI. Aim 2 relates brain activation (measured with high density EEG) to performance on these two tasks and measures of peripheral auditory function to identify differences in cortical activation in impaired listeners that are not solely a function of their poor peripheral input. Aim 3 conducts a longitudinal study to examine changes in the cortical systems for detecting generic auditory objects and speech in noise. We examine the same patients before implantation and 1, 3, 6 and 24 months post implantation using a combination of EEG, Positon Emission Tomography, (to achieve spatially precise measure of cortical activation)and behavioral measures. This will determine how the abilities to detect complex objects and speech in background noise?and the neural substrates that support these abilities?changes with experience with a hearing device.